/****************************************************************************
 *
 * Copyright 2016 Samsung Electronics All Rights Reserved.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 * http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing,
 * software distributed under the License is distributed on an
 * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND,
 * either express or implied. See the License for the specific
 * language governing permissions and limitations under the License.
 *
 ****************************************************************************/
/****************************************************************************
 * fs/vfs/fs_lseek.c
 *
 *   Copyright (C) 2008 Gregory Nutt. All rights reserved.
 *   Author: Gregory Nutt <gnutt@nuttx.org>
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 *
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in
 *    the documentation and/or other materials provided with the
 *    distribution.
 * 3. Neither the name NuttX nor the names of its contributors may be
 *    used to endorse or promote products derived from this software
 *    without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
 * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
 * COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
 * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
 * OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
 * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
 * ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
 * POSSIBILITY OF SUCH DAMAGE.
 *
 ****************************************************************************/

/****************************************************************************
 * Included Files
 ****************************************************************************/

#include <tinyara/config.h>

#include <sys/types.h>
#include <unistd.h>
#include <sched.h>
#include <errno.h>
#include <assert.h>

#include "inode/inode.h"

#if CONFIG_NFILE_DESCRIPTORS > 0

/****************************************************************************
 * Public Functions
 ****************************************************************************/

/****************************************************************************
 * Name: file_seek
 *
 * Description:
 *   This is the internal implementation of lseek.  See the comments in
 *   lseek() for further information.
 *
 * Parameters:
 *   file     File structure instance
 *   offset   Defines the offset to position to
 *   whence   Defines how to use offset
 *
 * Return:
 *   The resulting offset on success.  -1 on failure withi errno set
 *   properly (see lseek comments).
 *
 ****************************************************************************/

off_t file_seek(FAR struct file *filep, off_t offset, int whence)
{
	FAR struct inode *inode;
	int ret;
	int err = OK;

	DEBUGASSERT(filep);
	inode = filep->f_inode;

	/* File is not open */

	if (!inode) {
		err = -EBADF;
		goto errout;
	}

	/* Invoke the file seek method if available */

	if (inode->u.i_ops && inode->u.i_ops->seek) {
		ret = (int)inode->u.i_ops->seek(filep, offset, whence);
		if (ret < 0) {
			err = -ret;
			goto errout;
		}
	} else {
		/* No... Just set the common file position value */

		switch (whence) {
		case SEEK_CUR:
			offset += filep->f_pos;

		/* FALLTHROUGH */

		case SEEK_SET:
			if (offset >= 0) {
				filep->f_pos = offset;	/* Might be beyond the end-of-file */
				break;
			} else {
				err = EINVAL;
				goto errout;
			}
			break;

		case SEEK_END:
			err = ENOSYS;
			goto errout;

		default:
			err = EINVAL;
			goto errout;
		}
	}

	return filep->f_pos;

errout:
	set_errno(err);
	return (off_t)ERROR;
}

/****************************************************************************
 * Name: lseek
 *
 * Description:
 *   The lseek() function repositions the offset of the open file associated
 *   with the file descriptor fd to the argument 'offset' according to the
 *   directive 'whence' as follows:
 *
 *   SEEK_SET
 *      The offset is set to offset bytes.
 *   SEEK_CUR
 *      The offset is set to its current location plus offset bytes.
 *   SEEK_END
 *      The offset is set to the size of the file plus offset bytes.
 *
 *  The lseek() function allows the file offset to be set beyond the end of the
 *  file (but this does not change the size of the file). If data is later written
 *  at this point, subsequent reads of the data in the gap (a "hole") return null
 *  bytes ('\0') until data is actually written into the gap.
 *
 * Parameters:
 *   fd       File descriptor of device
 *   offset   Defines the offset to position to
 *   whence   Defines how to use offset
 *
 * Return:
 *   The resulting offset on success.  -1 on failure withi errno set properly:
 *
 *   EBADF      fd is not an open file descriptor.
 *   EINVAL     whence  is  not one of SEEK_SET, SEEK_CUR, SEEK_END; or the
 *              resulting file offset would be negative, or beyond the end of a
 *              seekable device.
 *   EOVERFLOW  The resulting file offset cannot be represented in an off_t.
 *   ESPIPE     fd is associated with a pipe, socket, or FIFO.
 *
 ****************************************************************************/

off_t lseek(int fd, off_t offset, int whence)
{
	FAR struct file *filep;
	off_t newpos;
	int errcode;
	int ret;

	/* Get the file structure corresponding to the file descriptor. */

	ret = fs_getfilep(fd, &filep);
	if (ret < 0) {
		errcode = -ret;
		goto errout;
	}

	DEBUGASSERT(filep != NULL);

	/* Then let file_seek do the real work */

	newpos = file_seek(filep, offset, whence);
	if (newpos < 0) {
		errcode = (int)-newpos;
		goto errout;
	}

	return newpos;

errout:
	set_errno(errcode);
	return (off_t)ERROR;
}

#endif
